1. Field of the Invention
The present invention relates to design methodologies used to implement integrated circuits, and more specifically to a method and apparatus for reducing time to measure constraint parameters of various components used in integrated circuits.
2. Related Art
Integrated circuits generally contain several components such as flip-flops and registers. It is often desirable to determine several characteristics of the components, for example, to determine a maximum clock speed at which an integrated circuit may be operated. Some of such characteristics of interest are constraint parameters. Constraint parameters generally refer to values specifying the minimum delay/duration between occurrence of two signals, with the reference signal being termed as a constraining signal and the other signal being referred to as a constrained signal.
For example, constraint parameters of interest with reference to sequential components (having memory, e.g. flip-flops) include setup time, hold time and minimum pulse width. As is well known, setup time generally refers to a minimal time duration a signal of interest (e.g., input signal as the constrained signal) is to reach a desired signal level ahead of a reference signal (constraining signal). Hold time refers to a minimum duration of time the signal of interest is to stay at the desired level after an edge of a clock signal, for example, to enable proper sampling. Pulse width refers to a minimum pulse duration the reference/constraining signal (e.g. clock signal) needs to stay at a desired signal level for a signal of interest to be sampled accurately by a sequential component.
A prior approach may consume a substantial amount of time to measure constraint parameters while designing integrated circuits. For example, in a common design cycle, a component is represented in the form of digital data, and input signals are applied to the component assuming a specific value for a constraint parameter. The output of the component is examined to determine if the component would operate accurately with the constraint parameter. Several iterations of applying input signals (with different values for the constraint parameter), may be performed to determine an accurate value for the constraint parameter. In general, the time to design an integrated circuit increases with an increase in the number of iterations.
In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.